Direction finder system



Patented Aug. 29, 1950 UNITED STA-LIES PATENT oreics RECT O ER; SXST M George Ia. Bellegninelli; New. York; N. 1., and Meli-n fi cim fie erki. ssien rs to; Fed r l" 'Iielecmimeuznirati n;v La orato i In N w- York,,N 1., a corporation of Delaware Applicationduly 1, 1946; Serial No. 880510 4 ClaIi (Cl. 343911 18) This invention relates generally to; direction finder systems, and particularly pertains trainsdicatoii circuits for-systems of that, character;

general, the invention. provides; axsystem for interpreting on a crossed. coil; meter signals derivemle from; a rotating loo-pv and. an; omnidirectionaltantenna; and-which'may: be operated, with out'vswitching at the-input ot the receiver byavirflue-lots the provision-ofssuitable;electronioswitche log and" distributing circuits, on novel, character hetweenl the. receiver output and the indicating meter.

Inrthe present system. signals derivectfrom the rotating loop, and omnidirectional; antenna, are dBtB tB -a ma re iver, which. may'itself-be ofany Sltitable character, the output; of: the, receiver being of sine; wave character; SW-itchma 1m.-

are derived at 90? intervals:ofrlooplrotatiom Wilioh; arequ-tilizedi to gate oul'r from every; cycle of the sine wave four meter control pulses;each of: which; has a p ak: amplitude which; ispr ional: o 1 theinstantaneous. amplitude ofr the 1 sine mare at, the instant of switching Means are amended or derivin ,directcurrent proportional tei he di fierenceinamnlitudes t alternate pulses. of resultant pair on direct; currents being aaeriiedeo a c i f the: crossed coilsmeten for Rimmin a; magnetic, field oriented; im accords nzc with Signal: azimu and which may: e r ns ated y he meteris; accordingly; anobjfi t of the-invention to p de: n ve d e for ndicating azimuthal direetion oii a signal.

It-,is-ancther object of the invention; to provide aasystem forproducing: directional indications, by translation; of; pulse signals hated 011133.01 other,- w se e re a r a total: dir tional-intonn ation bearing: signal.

A further obiect of the; invention; resides in the provision of devices for provid ng directional miiieat m ehmcae ofinovei; sw tching circuit coupled to a directional receiver output; and pariei larlr: w tch rcu s; which: u i ze selected sections; i hee v r utput:

Lt siancthcr' oieci: h invention to provide a; systemfon comparing the phases of a. rotating mehem aid u ew ha a; ine; wave signal comparison of selected portions-o1- the signal.

It: i i l; a f urihe ject of? the. inv n i n o memde-nor la eamatusf r measuring: the phase one wave signal? on. a crossed: coil: meter by translation and comparison of: selected; relatively nortions of: the signal.

"Eheiahove andzstill further objects: oi the iniiflntlani Willi become. apparent; upon study of: the

2, following detailed: description of, an embodiment ofthe invention, when taken. in.v conjunction with the accompanying drawings,

Fig. 1 of'which, is aschematic: circuit; diagram of an embodiment of our invention; and

2:0f which is a& curve used to explain the operation of thesystem.

In-.the drawings. the numeral l. denotes a loop antenna, which is: continuously rotated by means of a; motor 2=, the mechanical drive betweenthe loop and: the motor being symbolically: indicated by broken line 3. The signal output of the loop l; is detected; in; a receiver, generally identified by e numeral 4; and which maybe. of any suita le and lenovmcharacter, but which isprovided: with an output circuitin the form ofa diode 5; heating a plate 6 and; a cathode 1-, the latter beingconne ted to ground; through a, load resistor 8; byp sed bya condenser 9 for frequencies above that of the desired output signal. The; loop I is associated; in Well: known, fashion with an omnidirectional antenna lil; whereby the outputsignal derivable across. theresistance 8; will, be of: sine wave; character, as the loopvl rotates, the phase of the sine wavesignal being dependent. upon the; azimuthal direction of the incoming; radio signal from which the sil cywavesignal: ultimately derives;

'I-{he signal: appearing across the resistor 8; is coupled to anamplifier; tube l l by; means of couc n co d nse It n c u ling: resistance: 13:, the latter being; connected atanadjustable point M to the control grid !5 of the tube III:.. The time I; may'beza pentode, comprising a. suppressor grid i6; coupled directly to a cathode H, and: a screen grid l8; Icy-passed to ground over 9, con- ,enser t9; and supplied with operating-potential irom aiterminal 2il via EsI'GSlStAZlCi-B 2t. Lhe amplifier tube H is cathode-biasedby a resistance 22-, and issuppliedv with potential for the plate 23 thereof from a terminal 24 over a plate load resistance 25;

Iihe plateZ-G of theotube His coupledhymeans oft-a coupling condenser 26: to the control grid 21' of: a cathode. follower tetrode 28, having the usualasuppressor grid 29 and screen grid 30', the later being suppliedwith operating potential from a. terminal 31 over a resistance 32. Theplate 33 oh the-tube 28 is supplied, likewise, with operating potential-from a terminal 34 over aresistance 35, both plate anci screengrid' being by-passedto ground by condensers. A cathode follower arrangement is utilized because it is d sired tohave the sine waveadded: to asuitable D. 0; level, so that the instantaneous voltage is always positive,

at the same time that excessive unmodulated steady voltage is avoided. Correct bias for this purpose is applied to the grid 21 of the cathode follower 28 by means of a potentiometer arrangement comprising resistances 39 and 31 in series, the latter being adjustable, operating voltage for the potentiometer being tapped .from the terminal 2 1.

The combined positive potential and sine wave variation appearing across the cathode resistance 38, connected in circuit with the cathode 39 of the tube 28, is impressed over lead til to the plates of switching tubes 4|, 42, 43 and ill in parallel, these triodes being normally biased to cut-off,

and being switched on for short intervals only,

as will appear hereinafter.

tubes 4|, 42, 43 and 44 ar large time constant circuits Z5, 46, 41, 48, each circuit comprising a parallel resistance-capacitance combination, the resistances 69, 56, Si, 52 each being greater'than the internal resistance of its associated switching tube 4|, 42, 43 and M, respectively. By utilizing high relative values for resistances 49, 50, 52 the potentials across theseresistances may be maintained independent of the characteristics of tubes ll, 42, 43 and 44. The large time constants of the circuits 45-48, inclusive, serve to maintain steady voltage levels on the grids of D. C. ainplifier tubes 53, 55, 55, 56 in response to pulsed signals applied to the grid circuits 45-48, inclusive.

' Meter coil 51 is connected across the plates 58 and 59 of tubes 53 and 55, respectively, whereby the current flow in the coil 51 is a measure of the difference of voltage at the plates 58 and 59. Meter coil 6|] is likewise connected across the plates 6| and B2 of tubes 54 and 56, respectively, a current flow being maintained in the coil 69 proportional to the difference of potential of plates 65 and 62. The tubes 53-56, inclusive, are maintained stable by providing therefor highly degenerative cathode circuits, each comprising one of resistances 63-66, respectively, and variable resistances 51, 68, 69 being provided in circuit with the resistances G l-66, inclusive, to enable balancing of the D. C. amplifiers.

The curve 19, Fig. 2, indicates generally the potentials appearing across the cathode resistance 38 and which is impressed upon each of the plates of the tubes el-44, inclusive, and comprising a steady D. C. component 1| superimposed on the A. C. signal 10.

A series of pulses is applied in sequence to the tubes 4 of such magnitude and polarity as to cause these tubes to pass current momentarily. The points on curve it at which the pulses occur are equally spaced through the 360 duration of the curve, or'are spaced at 90 intervals, at points 12, 1t, '54 and 15. By applying to each of the control' grids 15, 11, 18, 19 of tubes 45-44, inclusive, control pulses of sufficient magnitude, each of tubes ll-t4, inclusive, is caused to pass a current pulse proportional to the value of potent al represented by the points 12-15, and since the long time constant circuits 35-48 maintain potentials appearing thereacross the tubes 53-56, maintain corresponding steady D. C. current flows and therefore corresponding stead plate potentials, for application, in the manner heretofore explained, to the meter coils 51 and 69.

Pulses for application to the grids 16-19 are provided b a pulse generating circuit generally denominated by the numeral 89, and comprising a wheel 8| having a periphery of variable and constantly increasing radius, the radius being sharply steeped at one point 82 of the periphery. Wheel 8| is rotated continuously in synchronism with the rotary motion of the loop I by means of motor 2,.the mechanical coupling between the motor 2 and the wheel 8| being indicated in conven tional manner by broken line 83.

Located adjacent the peripher of the Wheel 8|, in space quadrature, is a series of magnet coils 84, 85, 8B, 81, and the wheel 8| being constructed of magnetic materiaLpassage 0f the point 82 of the wheel 8| past each of the coils 84-81, inclusive, results in the induction of a sharp voltage pulse therein by reason of the extremel sharp variation of magnetic flux which then takes lace in the said coils.

The pulses produced in the coils 84-81 are time spaced, and occur at times corresponding with the times of the points 12-15, inclusive. The pulses are transferred via lines 88-9I to pulse amplifiers' 92-95,'respectively, the amplified pulses 96-99, inclusive, being then applied via transformer couplings EGO-I63, inclusive, to the grids 16-19 of the tubes ii-44. The use of transformer couplings to the grids 16-19 enables grid switching to be'carried on independently of voltages appearing in the cathode circuits of the tubes." Each of grids 15-19, inclusive, is provided with a D. C. restoring circuit consisting of a large condenser IM, and a large resistor I95. By virtue of the large B. C. time constant thus provided, the condensers I04 remain charged between pulses to the peak value of the applied pulses, maintaining a sufliciently large negative bias on the tubes 4|-44, inclusive, to maintain these tubes at cutoff; While a pulse is being impressed the instantaneous grid to cathode voltages of tubes 4I-44 become less negative, reducing to exactly zero-at the peak of the pulse, at which times'the tubes conduct.

It will be appreciated that great uniformity of tube characteristics and of circuit parameters in the switching channels is not required. The switching pulses provided in the various channels need not be all of the same amplitude, provided only that they are of sufficient amplitude to drive the switching tubes beyond the point at which grid'current flows. No mechanical contact mechanism is required for switching. The system has been found to provide accurate indications of azimuth, and is inherently straightforward and capable of ready adjustment and control.

While we have described one embodiment'of our invention, it will be realizedthat various modifications in the arrangements of the combination and in the details of its structure and the choice of its elements ma be resorted to with out violating the spirit of the invention as defined by the appended claims.

1. In a direction finding receiver for radiant energy, the combination comprising a directive antenna system, means for effectively periodically rotating the directivity of said antenna system, asignal receiver for said antenna means'including a detector for deriving a periodic signal wave from radiant energy received by said antenna having the-periodicity of the rotation of the directivity of said antenna system, means for adding a direct'current' component to said signal wave, means for sampling said added direct cur-- rent component and signal wave to derive a plurality of pulses for each period of said signal wave, an indicating meter having two field coils, said coils'being coupled for combining given ones of said pulses for the purpose of amplitude comparison to indicate the direction of arrival of said radiant energy at said receiver.

2. In a direction finding receiver for radiant energy, the combination comprising a directive antenna system, means for effectively periodically rotating the directivity of said antenna system, a signalreceiver for said antenna means including a detector for deriving a periodic signal wave from radiant energy received by said antenna having the periodicity of the rotation of the directivity of said antenna system, means for adding a direct current component to said signal wave, means for sampling said added direct current component and signal wave to derive a plurality of pulses for each period of said signal'wave,

said sampling means comprising means for providing gating pulses in synchronism with the rotary antenna, a plurality of switchin tubes and means for applying said signal wave and said gating pulses to said switching tubes, and means for combining given ones of said pulses for the purpose of amplitude comparison to indicate the direction of arrival of said radiant energy at said receiver.

3. A direction finding system for transmitted radiant energy comprising a directive antenna system, means for cyclically varying the directivityof said antenna system, means responsive to the reception of energy by said antenna system and controlled by cyclically variable directivity to said antenna system for producing a cyclic signal wave, a source of gatin pulses synchronized with said means for sampling said wave at spaced portions in its cycle, each of said pulses corresponding with a predetermined different directivity of said antenna system, normally blocked separate switching means corresponding to each of said, predetermined directivity positions of the antenna system, an indicator coupled to said switching means for applying said signal wave to said indicator for the duration of the gating pulses, said indicating means serving to compare the amplitudes of said sampled portions for determining the duration of the arrival of said energy at said antenna system.

4. In a direction finding receiver for radiant energy, the combination comprising a directive antenna, means for effectively rotating the directivity of said antenna at a given speed, a signal receiver for said antenna including a signal detector for deriving a sinusoidal signal wave from the energy received by said antenna the phase of which is dependent on the azimuthal position of said antenna, means for processing said sinusoidal wave to derive a corresponding uni-directional variable signal, means for combining said sine wave and said unidirectional signal, means for providing a series of gating pulses for each cycle of said sine wave driven by said rotating means, signal translating circuit means for each of said cyclical gating pulses including an electronic switch for each circuit, means for applying said variable signal to said electronic switches in parallel, and means for combining the portions of said variable signal gated by alternate of said pulses for the purpose of comparison including the two coils of a direction indicating meter.

GEORGE L. PEILEGRINELLI. MELVIN KLEIN.

REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Number Name Date 2,263,377 Busignies et al Nov. 18, 1941 2,272,607 Higcnnet Feb. 10, 1942 2,380,929 Ahier et al Aug 7, 1945 2,388,262 Ganiayre et al Nov. 6, 1945 2,405,930 Goldberg et a1. Aug. 13, 1946 2,415,566 Rhea Feb. 11, 1947 2,421,663 Tolson June 3, 1947 a combining 

